Wednesday, February 11, 2009

Precise observation of uranium by Kaguya GRS

Color-coded map of the Uranium net counting rate over the entire lunar surface as measured by Kaguya's Gamma Ray Spectrometer. It was drawn using simple cylindrical projection at 15° per pixel resolution. With contour based on albedo data from Clementine (1994) roughly shows boundaries between maria and highlands, and Kaguya GRS data appears to show a relatively high spike in the Uranium signature centered near Copernicus and its ejecta blanket, northeast to Eratosthenes and along the mare buried boundary of Montes Carpatus separating Mare Imbrium and Oceanus Procellarum (Lunar and Planetary Science Conference XL, #1855- Fig. 3).

The Final Announcement heralding the Lunar and Planetary Science Institute's 40th Annual Conference (March 23-27 at The Woodlands, Texas) has been accompanied by a vast menu of presentations and abstracts fulfilling growing expectation of new and exciting revelations from the world of planetary sciences. The program does not disappoint, highlighted, but not limited to, new analysis from on-going experiments at Earth's Moon and Mars.

Two full sessions at the conference, for example, are devoted to China's Change'E 1, Japan's Kaguya (SELENE 1) and, surprisingly because it only arrived in lunar orbit only last November, India's Chandrayaan 1.

Based on a quick glance over those abstracts, the public are sure to be treated to headline-generating stories, some of which have very recently made ink. The report of the the oldest Zircon yet confirmed and of magnetism found in samples and lunar meteorites has been perhaps a bit overblown. Fossil and anomalous local magnetism on the Moon has been a matter of record since the Apollo Era, as was the age of the oldest lunar rocks, the theories of a Global Magma Ocean, etc.

Rumors had also been floating around, whispered in conspiratorial tones, that Japan's Kaguya orbiter has found the precise location of Uranium on the Moon. Abstract 1855 of the Lunar and Planetary Science Conference XL (2009) confirms this claim, though the map accompanying the article has the same resolution as the Apollo sub-satellites of 1972.

The introduction to the consortium of JAXA scientist-authored paper says, "The SELENE mission is the first to employ a germanium (Ge) detector to observe lunar gamma rays. With a superior energy resolution, the SELENE Gamma-Ray Spectrometer (GRS) has uniquely identified many elements that constitute the lunar surface such as (potassium, thorium, uranium, oxygen, magnesium, aluminium, silicon, calcium, titanium and iron) in the upper layer of (around 60 grams per square centimeter) with high precision. With the SELENE GRS, the global distribution of uranium on the lunar surface was revealed for the first time. Together with those of other radioactive nuclides, potassium and thorium," providing important information regarding the Moon’s thermal history."

Lunar and Planetary Science XL (2009)

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